Sometimes situations arise during a call between an operator in a call center and a customer, for example, when an inexperienced operator is in a confused state due to a complaint or the like from the customer, and the inexperienced operator finds it difficult to give an appropriate response. So that an experienced operator can assist the inexperienced operator who is in a confused state in such cases, technology exists that can be employed to determine whether or not the operator is in a confused state. This technology determines the intention of a speaker based on changes in meter in the call audio. For example, in this technology, the speaker is detected as having doubts, namely, that there is a possibility of the speaker being in a confused state, when a sustained utterance duration is short and the fundamental frequency thereof is inflected upward.